Why Water Retention Occurs After Resistance Training and Why You Shouldn't Worry

You feel great! You cleaned up your diet, renewed your gym membership and knocked out your first couple of killer workouts. Never mind that you're so sore you can hardly climb on the scale. It's worth it just to see the numbers go ... up? Before you throw up your hands in despair and break out a pint of rocky road, take a deep breath and relax. It's just a little water retention caused by delayed-onset muscle soreness.

Read more: Does Strength Training Cause Water Retention?

DOMS, or delayed-onset muscle soreness, is a common phenomenon marked by muscle pain ranging from mild to debilitating and manifesting 24 to 48 hours after your workout. Besides muscle soreness, other symptoms of DOMS include loss of strength, decreased range of motion, decreased neuromuscular function, mild inflammation and an increase of 2 to 3 pounds or more in body weight.

DOMS is common in individuals who are new to resistance training or as a response to a change in exercise routines, such as adding challenging, new exercises or increasing weight loads.

Once thought to be caused by the accumulation of lactic acid in the muscle cells as a byproduct of ATP metabolism, researchers now believe that structural damage to the muscle cells caused during the muscle lengthening, or eccentric, phase of exercise is the cause of DOMS.

Exercise physiologist Len Kravitz, Ph.D., of the University of New Mexico explains that the tearing of muscle tissue and the rupture of muscle cells initiates an inflammatory response that peaks 24 to 36 hours after exercise. As a part of this response, the hormones ADH and aldosterone cause the kidneys to retain water. After a few days, balance is restored and water weight is eliminated.

Read more: Water Retention in Muscles After Exercise

While DOMS is not completely preventable, symptoms may be diminished. A pre-exercise warmup may minimize damage to muscle tissue. Include a general warmup that uses large muscle groups, like walking or jogging, to elevate core temperature and warm the muscles followed by a specific warmup for the muscles to be targeted during exercise, like a set using light weights before loading up.

Practicing good technique will also minimize tissue damage. Muscles are under the most tension during eccentric movement — sometimes called the negative part of an exercise, as the muscle is lengthening but still contracting. Lifting more weight than you can control in the muscle-lengthening phase places more stress on muscles and joints as gravity takes over.

Taking nonsteroidal anti-inflammatory drugs, or NSAIDs, like ibuprophen, has been a common practice for treating DOMS. However, according to Len Kravitz, Ph.D., NSAIDs do not appear to be an effective treatment. But rest, stretching and massage therapy may help.

DOMS usually diminishes or disappears completely within three to four days of your exercise session. Post-exercise pain that lasts longer than a week may indicate damage that requires medical attention. Meanwhile, you may want to steer clear of the scale for a few days after vigorous weight training.